Set up S3 sleep state in Vista for significant power savings

Unlike older power management modes, S3 sleep state knocks your computer out almost cold, maintaining just enough alertness for you to wake it up. Your computer will typically draw only about 2 to 3 watts of power while it sleeps, and it will take only a few seconds to pick up where you left off before it went dormant. Justin James explains what you need to know about creating an S3 power plan.

With newer computers come higher power bills. Modern
processors, RAM chips, and hard drives consume much more power than their
predecessors did, and the trend is likely to continue. While hardware
manufacturers continue to work at reducing the levels of power consumption, the
reduction is usually just a reduction in the leap from the previous generation,
as opposed to a net loss. However, you can reduce the amount of power used by
the PC when you are not there, and on some PCs, you can even change how much power
is used when you're using it.

This is where the S3 sleep state comes in. In older power-saving
modes (S1 sleep state), the computer could shut down some components, such as
the hard drives and the monitors, after a period of time to reduce power usage.
However, the CPU, fans, and other internal components continued to run at full
speed. With the S3 power management, your computer is nearly out cold. It
maintains a minimum amount of alertness, just enough to wait for you to wake it
up. Unlike older "hibernate" schemes, the computer is not actually
off with its state saved, it is still on. When you wake it up, you don't need
to wait for the BIOS to post or the operating system to come up enough to
restore the saved state. Instead, your computer takes only a few seconds to be
ready for work, right where you left off. During this deep sleep, the computer
will typically draw about 2 to 3 watts of power — a far cry from the small
reduction in power usage with the older S1 sleep state.

Using S3 sleep state in Windows XP

S3 sleep state is enabled by default in Windows Vista. In Windows
XP, though, a Registry key change is needed. TechRepublic offers a download that will change this
Registry setting for you. This article looks at Windows Vista, but
it's applicable to Windows XP as well. The Power settings section of the
Control Panel is a bit different, but the rest of the settings should be the
same.

Make sure S3 sleep state is enabled in the BIOS

Some BIOSes require S3 sleep state
to be enabled or configured within the BIOS before the operating system can
take advantage of it. Many modern motherboards do not require (or even contain
settings for) this configuration. Your best bet is to check your BIOS'
settings, looking in particular at the Power section. Key words to look for are
"S3," "Sleep," "Wakeup," and "Resume." Figure A shows an American Megatrends BIOS and its S3 settings section.

Figure A

Enabling Wake On LAN (optional)

This step is optional. Wake On LAN is a setting that allows
the computer's NIC(s) to bring the PC out of the S3 sleep state upon receipt of
a Magic Packet. If you have no reason to wake the PC up without being
physically present, you can skip this step. If you want to be able to remotely
access the PC (for file sharing, Remote Desktop, or other uses), you'll want to
enable this functionality.

Open Device Manager.

Find the NIC that you want to be able to perform Wake On
LAN and open its properties sheet.

Go to the Power Management tab of the Properties sheet.

Check Allow This Device To Wake The Computer (Figure B). If you find that your
computer will not stay in the sleep state, you may need to check Only Allow
Management Stations To Wake This Computer.

Figure B

Creating your power plan

Open System and Maintenance in Control Panel and select
Power Options.

Click Create A Power Plan on the left sidebar (Figure C).

Select the power plan you want to start with. (In this
example, I will use High Performance.)

Name your plan and click Next (Figure D).

Choose your initial basic settings and click Create (Figure E).

Figure C

Figure D

Figure E

Editing the new power plan

Click Change Plan Settings (Figure F).

Figure F

Click Change Advanced Power Settings.

To change Require A Password On Wakeup, click Change
Settings That Are Currently Unavailable.

Set the Turn Off Hard Disk After option to a value less
than or equal to the time for the PC to sleep, for maximum power savings. Note: having the hard drives turn off while
you are still using the computer can cause significant slowdown as they spin
back up. It is recommended to set this equal to the time needed to go to sleep.

Set Sleep After equal to the time you set on the basic
power plan settings screen.

Make sure that Allow Hybrid Sleep is set to On. This allows
a combination of S3 (low power) and S4 (Hibernate) to be used. That way, if the
computer loses power, no work is lost. This is, of course, at the expense of a
small bit of hard drive space. In my opinion, there is no reason not to use
this setting.

Set Turn off Display After to the same value entered on the
basic power plan settings screen.

Click OK on the Advanced Power Settings screen.

Click the Save Changes button on the Basic Power Plan Settings
screen.

To minimize the CPU's power draw under light load, edit the
Minimum Processor State setting under Processor Power Management. To scale it
back even under heavy load, change the setting for Maximum Power State.

Testing the new settings

To test the new settings, simply leave the computer alone
for the specified amount of time. You will hear the computer get extremely
quiet; this is because all of the fans and hard drives have been stopped. If
you still hear fans or drives, go back and check your settings, particularly
your BIOS settings.

Waking up the computer

The computer will appear to be off. You will need to press
the power button, a mouse button (at least with an optical mouse; a mechanical
mouse may work with a jiggle), or tap the keyboard to get the computer to turn
on. After waking, the computer will spin up the drives and the fans, and in
under 10 seconds, you should see your desktop or the login screen, depending
upon whether you chose for the computer to require a password upon waking. (The
default setting is to require a password.)

If you are looking to wake the computer up remotely (for
example, to connect to it via Remote Desktop), you will need to send a Magic
Packet to the PC. The Magic Packet is a specially designed IP packet (usually a
UDP datagram) that tells the NIC to wake the computer up. This Magic Packet
needs the MAC address of the NIC, so be sure to have this information handy
when configuring or using a Wake On LAN utility. The easiest place to get this
information is to click the Details button on the Network Connection Details
screen (Figure G) and look under Physical
Address. Alternatively, you can run the command ipconfig /all from the command line to retrieve the MAC address (Figure H) and look for the entry for Physical
Address.

Figure G

Figure H

A variety of utilities are available for sending the Magic
Packet. If you're going to be waking the computer up only from within the
network, you'll need the broadcast address for your local network. If you plan
to wake the computer up from outside of your local LAN through the Internet,
you'll need to configure your router to forward the Wake On LAN port (usually
port 9 or port 7) on the external interface to the IP address that is the
internal broadcast address. Not every router supports port forwarding to a
broadcast address, so test this on your router before expecting it to work.

Because a broadcast address is used and the Magic Packet is
keyed with the PC's MAC address, you can have
multiple computers within the network set to go to sleep and selectively wake
them up. You do not necessarily need to use the broadcast address if you can be
assured that the PC will always have the same address (such as in a static IP
address scheme or if the DHCP server keeps a reservation for that PC). But
generally speaking, using the broadcast address makes the most sense.

Some free utilities to perform Wake On LAN are:

Depicus: A Wake On LAN utility written
in .NET. There is also a Web-based version, which you can use on the company's
Web site or download and install on your own Web site. Additionally, non-.NET versions
are available, including a Macintosh version. Note: the Web site and the software will send to the broadcast for the
network.